﻿using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Reflection;

namespace Masuit.Tools.Systems
{
	/// <summary>
	/// 枚举扩展类
	/// </summary>
	public static partial class EnumExt
	{
		private static readonly ConcurrentDictionary<Type, Dictionary<int, string>> EnumNameValueDict = new ConcurrentDictionary<Type, Dictionary<int, string>>();
		private static readonly ConcurrentDictionary<Type, Dictionary<string, int>> EnumValueNameDict = new ConcurrentDictionary<Type, Dictionary<string, int>>();
		private static ConcurrentDictionary<string, Type> _enumTypeDict;

		/// <summary>
		/// 获取枚举对象Key与显示名称的字典
		/// </summary>
		/// <param name="enumType"></param>
		/// <returns></returns>
		public static Dictionary<int, string> GetDictionary(this Type enumType)
		{
			if (!enumType.IsEnum)
			{
				throw new Exception("给定的类型不是枚举类型");
			}

			var names = EnumNameValueDict.ContainsKey(enumType) ? EnumNameValueDict[enumType] : new Dictionary<int, string>();
			if (names.Count == 0)
			{
				names = GetDictionaryItems(enumType);
				EnumNameValueDict[enumType] = names;
			}

			return names;
		}

		private static Dictionary<int, string> GetDictionaryItems(Type enumType)
		{
			var enumItems = enumType.GetFields(BindingFlags.Public | BindingFlags.Static);
			var names = new Dictionary<int, string>(enumItems.Length);
			foreach (FieldInfo enumItem in enumItems)
			{
				int intValue = (int)enumItem.GetValue(enumType);
				names[intValue] = enumItem.Name;
			}

			return names;
		}

		/// <summary>
		/// 获取枚举对象显示名称与Key的字典
		/// </summary>
		/// <param name="enumType"></param>
		/// <returns></returns>
		public static Dictionary<string, int> GetValueItems(this Type enumType)
		{
			if (!enumType.IsEnum)
			{
				throw new Exception("给定的类型不是枚举类型");
			}

			var values = EnumValueNameDict.ContainsKey(enumType) ? EnumValueNameDict[enumType] : new Dictionary<string, int>();
			if (values.Count == 0)
			{
				values = GetValueNameItems(enumType);
				EnumValueNameDict[enumType] = values;
			}

			return values;
		}

		private static Dictionary<string, int> GetValueNameItems(Type enumType)
		{
			var enumItems = enumType.GetFields(BindingFlags.Public | BindingFlags.Static);
			var values = new Dictionary<string, int>(enumItems.Length);
			foreach (var enumItem in enumItems)
			{
				values[enumItem.Name] = (int)enumItem.GetValue(enumType);
			}

			return values;
		}

		/// <summary>
		/// 获取枚举对象的值内容
		/// </summary>
		/// <param name="enumType"></param>
		/// <param name="name"></param>
		/// <returns></returns>
		public static int GetValue(this Type enumType, string name)
		{
			if (!enumType.IsEnum)
			{
				throw new Exception("给定的类型不是枚举类型");
			}

			Dictionary<string, int> enumDict = GetValueNameItems(enumType);
			return enumDict.ContainsKey(name) ? enumDict[name] : enumDict.Select(d => d.Value).FirstOrDefault();
		}

		/// <summary>
		/// 获取枚举类型
		/// </summary>
		/// <param name="assembly"></param>
		/// <param name="typeName"></param>
		/// <returns></returns>
		public static Type GetEnumType(Assembly assembly, string typeName)
		{
			_enumTypeDict ??= LoadEnumTypeDict(assembly);
			return _enumTypeDict.ContainsKey(typeName) ? _enumTypeDict[typeName] : null;
		}

		/// <summary>
		/// 根据枚举成员获取Display的属性Name
		/// </summary>
		/// <returns></returns>
		public static string GetDisplay(this Enum en)
		{
			var type = en.GetType(); //获取类型
			var memberInfos = type.GetMember(en.ToString()); //获取成员
			if (memberInfos.Any())
			{
				if (memberInfos[0].GetCustomAttributes(typeof(DisplayAttribute), false) is DisplayAttribute[] attrs && attrs.Length > 0)
				{
					return attrs[0].Name; //返回当前描述
				}
			}

			return en.ToString();
		}

		private static ConcurrentDictionary<string, Type> LoadEnumTypeDict(Assembly assembly)
		{
			return new ConcurrentDictionary<string, Type>(assembly.GetTypes().Where(o => o.IsEnum).ToDictionary(o => o.Name, o => o));
		}

		/// <summary>
		/// 获取枚举值的Description信息
		/// </summary>
		/// <param name ="value">枚举值</param>
		/// <param name ="args">要格式化的对象</param>
		/// <returns>如果未找到DescriptionAttribute则返回null或返回类型描述</returns>
		public static string GetDescription(this Enum value, params object[] args)
		{
			var type = value.GetType();
			if (!Enum.IsDefined(type, value))
			{
				return Enum.GetValues(type).OfType<Enum>().Where(value.HasFlag).Select(e =>
				{
					var member = type.GetField(e.ToString());
					var description = member.GetCustomAttributes(typeof(DescriptionAttribute), false) is DescriptionAttribute[] attrs && attrs.Length != 0 ? attrs[0].Description : e.ToString();
					return args.Length > 0 ? string.Format(description, args) : description;
				}).Join(",");
			}

			var member = type.GetField(value.ToString());
			var description = member.GetCustomAttributes(typeof(DescriptionAttribute), false) is DescriptionAttribute[] attributes && attributes.Length != 0 ? attributes[0].Description : value.ToString();
			return args.Length > 0 ? string.Format(description, args) : description;
		}

		/// <summary>
		/// 获取枚举值的Description信息
		/// </summary>
		/// <param name ="value">枚举值</param>
		/// <param name ="args">要格式化的对象</param>
		/// <returns>如果未找到DescriptionAttribute则返回null或返回类型描述</returns>
		public static IEnumerable<TAttribute> GetAttributes<TAttribute>(this Enum value) where TAttribute : Attribute
		{
			var type = value.GetType();
			if (!Enum.IsDefined(type, value))
			{
				return Enum.GetValues(type).OfType<Enum>().Where(value.HasFlag).SelectMany(e => type.GetField(e.ToString()).GetCustomAttributes<TAttribute>(false));
			}

			return type.GetField(value.ToString()).GetCustomAttributes<TAttribute>(false);
		}

		/// <summary>
		/// 获取枚举值的Description信息
		/// </summary>
		/// <param name ="value">枚举值</param>
		/// <returns>如果未找到DescriptionAttribute则返回null或返回类型描述</returns>
		public static EnumDescriptionAttribute GetEnumDescription(this Enum value)
		{
			return GetEnumDescriptions(value).FirstOrDefault();
		}

		/// <summary>
		/// 获取枚举值的Description信息
		/// </summary>
		/// <param name ="value">枚举值</param>
		/// <returns>如果未找到DescriptionAttribute则返回null或返回类型描述</returns>
		public static NullableDictionary<string, (string Description, string Display)> GetTypedEnumDescriptions(this Enum value)
		{
			return GetEnumDescriptions(value).ToDictionarySafety(a => a.Language, a => (a.Description, a.Display));
		}

		/// <summary>
		/// 获取枚举值的Description信息
		/// </summary>
		/// <param name ="value">枚举值</param>
		/// <returns>如果未找到DescriptionAttribute则返回null或返回类型描述</returns>
		public static IEnumerable<EnumDescriptionAttribute> GetEnumDescriptions(this Enum value)
		{
			if (value == null)
			{
				throw new ArgumentNullException(nameof(value));
			}

			var type = value.GetType();
			if (!Enum.IsDefined(type, value))
			{
				return Enum.GetValues(type).OfType<Enum>().Where(value.HasFlag).SelectMany(e => type.GetField(e.ToString()).GetCustomAttributes(typeof(EnumDescriptionAttribute), false).OfType<EnumDescriptionAttribute>());
			}

			return type.GetField(value.ToString()).GetCustomAttributes(typeof(EnumDescriptionAttribute), false).OfType<EnumDescriptionAttribute>();
		}

		/// <summary>
		/// 扩展方法：根据枚举值得到相应的枚举定义字符串
		/// </summary>
		/// <param name="value"></param>
		/// <param name="enumType"></param>
		/// <returns></returns>
		public static String ToEnumString(this int value, Type enumType)
		{
			return GetEnumStringFromEnumValue(enumType)[value.ToString()];
		}

		/// <summary>
		/// 根据枚举类型得到其所有的 值 与 枚举定义字符串 的集合
		/// </summary>
		/// <param name="enumType"></param>
		/// <returns></returns>
		public static NameValueCollection GetEnumStringFromEnumValue(Type enumType)
		{
			var nvc = new NameValueCollection();
			var fields = enumType.GetFields();
			foreach (FieldInfo field in fields)
			{
				if (field.FieldType.IsEnum)
				{
					var strValue = ((int)enumType.InvokeMember(field.Name, BindingFlags.GetField, null, null, null)).ToString();
					nvc.Add(strValue, field.Name);
				}
			}

			return nvc;
		}
	}
}
